restraint

Restraint is the act of holding something back. For example, if you exercise restraint over your emotions, you won't burst out into tears in public.

As you may have guessed from its similar spelling, the word restraint comes from the verb restrain, which in turn comes from the Latin word restringere, meaning "draw back tightly, confine, check." When talking about an object, a restraint is a device used to maintain control of something. For example, if your leg is operated on, the doctors will use a restraint to hold it still.